Veneer molding process



March 2, 1943. c. u. GRAMELSPACHER 2,312,332

VENEER HOLDING PROCESS Filed Aug. 11, 1939 4 Sheets-Sheet 1 l Jmawhv cmgsucs usmnnsmcnen,

c. u. GRAMELSPACHER 2,312,332

March 2, 1943.

VENEER MOLDING PROCESS Filed Aug. 11, 1939 4 Sheets-Sheet 2 4 i na? 1 MW LWX .9 u

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March 2, 1943. c. u. GRAMELSPACHER 2,312,332

VENEER MOLDING PROCESS Filed Aug. 11, 1939 4 SheetsPSheet 3 V Jrvum-u cuuumc: usmnqumcnm,

March 2, 1943. c. u. GRAMELSPACHER VENEER MOLDING PROCESS Filed Aug. 11, 1959 4 Sheets-Sheet 4 .flELll.

H m a H a W W Z i Patented Mar. 2, 1943 OFFICE VENEER MOLDING PROCESS Clarence U. Gramelspacher, Jasper, Ind. Application August 11, 1939, Serial No. 289,691

4 Claims.

This invention relates to a process for forming individual sheets of wood veneer or of very flexible plywood (say 2 or 3-ply) into articles of desired configuration and more particularly to a process of forming said sheets into articles embodying simple or compound curves. The present invention eliminates the necessity for first making a flat section of plywood and then bending it into the desired shape by saw-kerilng, corrugating and the like. In a still more particuiar aspect, the present invention relates to a veneer molding process wherein pressure is exerted on the outside of the sheets to be joined and forming pressure is yieldingly exerted from the inside of the sheets outwardly as by means of an expansible bag. Pressure of any kind can be used for these purposes.

The principal object of the present invention is to devise a method of forming veneer or flexible plywood sheets which are free to slide relative to one another by exerting pressure outwardly from inside of the sheets, while holding the sheets from their exterior in such manner that the inwardly exerted pressure is effective; the pressure exerted from the outside cooperates with the pressure exerted from the inside to produce an article the configuration of which corresponds exactly to that of the outer mold member so that the shape and dimensions of the article are accurately known in advance.

Another object is to carry out a process of the foregoing type wherein the inner mold member is in the form of an expansible bag member which is expanded evenly outwardly over the entire inside area of the sheets to be formed by means of a fluid under pressure admitted thereto, such as steam, air or other gas under pressure, or a liquid such as water, oil, or other suitable hydraulic liquid under pressure.

Another object is to devise a process of the type above set forth wherein at least one of each pair of adjoining surfaces of the sheets of veneer or thin plywood is precoated with an adhesive which is either liquid at the time of assembly or which becomes liquid under the conditions of molding; this liquid adhesive acts as a lubricant allowing the individual sheets to slide relative to one another, this shifting enabling the quick formation of a more perfect article wherein none of the individual sheets is under stress or tension relative to any other sheet, absolute concentricity throughout the curves being obtained.

Yet another obiect is to carry out a process of the type described above wherein heat is applied to the sheets during the molding process in order to dry and harden the glue or to set the resin where a thermo-setting resin adhesive is employed; this heat may be applied to the sheets from either the outside or the inside; a convenient method is to employ cored outer mold members and to pass a suitable hot fluid under pressure into the expansible bag to serve the dual purpose of expanding the same to shape the article and. to heat the sheets constituting the article.

Another object is to carry out a process of the foregoing type wherein a base member connects the ends of the veneer or plywood sheets.

Another object is to provide an expansible bag of variable thickness or consistency so that when pressure is exerted against the inside of the clamping iorm this pressure will be exerted evenly over the entirearea; for example, if a spherical bag is used in a rectangular article the pressure on the corners will not be as great as the pressure on the sides; however, I have discovered that this efiect can be compensated for to a large extent by designing the bag so that the portions for contacting the sides are relatively thick and progressively thin out to the portions which contact the corners.

Another object is to devise apparatus for carrying out the foregoing process.

Another object is to devise a method and apparatus for molding internally irregularly shaped articles which. involves utilization of a rigid mold member contacting on one side the irregular surface, such as an internal insert, and on the other side. which is smooth, the expansible bag.

Other objects will more fully hereinafter appear.

In the accompanying drawings:

Figure l is a perspective showing the individual sheets of veneer, or single laminations. with the coating of adhesive on at least one face of each, ready for molding. Instead of coating each lamination, alternate laminations may be coated on both sides.

Figure id is a vertical section through one of the coated veneer sheets of Figure 1.

Figure 2 is a perspective showing individual sheets of coated plywood, ready to be molded.

Figure 2a is a vertical section through a coated plywood sheet of Figure 2.

Figure 3 isa horizontal section through a mold for a four sided radio cabinet, as an example, having a baseboard and shows the individual veneer sheets in place with the outer mold members about to be clamped about them and with the expansible rubber bag inner mold member in collapsed form. The showing oi a radio cabinet is merely an example of an article which can be molded by this process.

Figure 4 is a horizontal section on the line II of Figure 5, looking in the direction of the arrows, and shows the mold of Figure 3 closed I and the bag expanded; the bag is shown as thinned in those areas where expansion is most extensive.

Figure 5 is a vertical, transverse section on the line I! of Figure 4, looking in the direction of the arrows; in this figure the article has been completely formed, the mold cover opened, the cabinet front has been inserted on the top thereof, and the mold cover has been closed to cement the front in place; this figure shows the inlet to the expansible bag inner mold member and the guide for the outer front wall of the mold; this shows merely one way of applying the front of the cabinet.

Figure 6 is a horizontal sectional view of a modification in which no baseboard is employed; the ends of each veneer sheet form a butt Joint and these joints are staggered around the article, one in the center of each side thereof, to prevent the formation of a weak joint; in this view the molding is done without heat, uncored outer mold members being shown.

Figure 7 is a detail section on the line 1-1 of Figure 6, looking in the direction of the arrows, and shows the external clamping and locking means for the end walls.

Figure 8 is a horizontal section showing a modification in which the article does not form a complete enclosure.

Figure 9 is a horizontal section showing a modification in which an insert extends inwardly from the inner face of the article causing sharp internal angles, a rigid auxiliary mold member being provided to present a smooth face to the expansible bag and to transmit the pressure thereof evenly to the insert and the plywood portion of the article.

Figure 10 is a perspective view showing the laminations of veneer cut for a still further modification: this view is also an example of the procedure wherein alternate laminations are adhesively coated on both sides and the other alternate laminations are uncoated.

Figure 11 is a vertical sectional view through the middle lamination of Figure 10.

Figure 12 is a vertical sectional view similar to Figure 5, showing the preparation of an article such as a five sided article from the flat individual sheets of Figure 10.

Referring first to Figures 3 to 5 of the drawings, reference numeral l designates a supporting base for the molding device. To base I is attached by means of bolts I a vertical rear wall I which is stationary and forms a rear mold member. Hinged to rear wall I by means of hinges l are end walls I which are adapted to be swung outwardly until parallel with rear wall 2, or even further if desired, to allow the lamination assembly to be inserted in the mold. A front mold wall 8 is slidably mounted on base I by means of a plurality of elongated pins I projecting upwardly from and integral with base I (see Figure 5) and which are received within slots I in the bottom of wall 6. Slots 8 are elongated in the direction in which front wall 6 is slidable.

Front wall 8 is provided on its inward face with an outward recess It to receive the baseboard ll of the exemplary radio cabinet or other object to be molded. Front wall I and rear wall 2 are provided with inwardly extending curved corner mold members it which may be integral with the walls and which serve to impart the desired curved configuration to the corners of the cabinet. Front wall 8, rear wall 2 and end walls I are provided with cored passageways II which are adapted to be supplied with steam or other hot fluid by an inlet pipe ill for the purpose of heating the laminations during molding. Any suitable means (not shown) such as a resilient gasket may be provided to seal the passages at the point where they interconnect between adjacent mold walls.

A moldcover i2 hinged at it to rear wall 2 is adapted to be clamped down over the closed mold preparatory to molding and locked in its clamped position by means of links II pivoted to the forward edge of cover if adapted to be locked over hook members it fixedly mounted on the front face of front wall G by hand locking members i1 pivotally carried on the lower end of links II.

Front wall 8 is adapted to be moved inwardly into clamping position against the ends it of inwardly swung end walls I thereby clamping the end walls I tightly between rear wall 2 and front wall 6. To this end, a cam clamping member it having a handle II is pivoted about a vertical pivot member 20 fixedly mounted in base i. Cam member I! is adapted to engage the front face of front wall 8 and to urge wall 6 inwardly into a firmly -clamped position and to lock it in this position by reason of the frictional engagement of cam I! with wall 8.

End walls I are adapted to be locked in their inward position by means of circular heads 22 journalled on the upper ends of shanks 23 which extend downwardly (see Figure 7) through elongated curved slots 24 in base platel into hinged engagement 2Ia with a manually operated handle 2S pivoted so as to be swingable vertically about a member 28 which is pivoted so as to be swingable horizontally by a pivot member 21 extending pivotally upwardly into a recess in base plate I. A circular recess 28 is provided at the outermost end of curved slot 2| to receive circular head 22 when the handle 25 is at its outermost position so that; the top of head 22 may be flush with or below the upper surface of base I whereby interference with. outward swinging of end walls I is prevented. A catch 29 is provided on the under face of base i into which handle 28 may be inserted to lock the same in clamped position thereby locking mold walls I in their inward position. To unlock walls I, handle 25 is raised vertically out of catch 29 and is then swung outwardly and downwardly, thereby allowing walls I to move freely outwardly. Hinge IIa being at right angles to handle II allows shank 23 to remain vertical as handle 25 is raised and lowered, but prevents it from sliding out slot II due to the pressure of the mold wall.

While mechanical means is shown for clamping end walls I and front wall I and so designed as to give increased leverage as the wall close in on the article to be molded, it will be apparent that any external means for exerting clamping pressure inwardly may be employed, such as suitable hydraulic or pneumatic means.

An expansible bag 30 of rubber or the like is provided within the mold cavity and designed when expanded to exert pressure outwardly on the article forcing the laminations outwardly against the externally clamped mold members. Bag 30 has an inlet 3|, which extends downwardly through base I, and may be semi-permanently left in the mold by means of nuts 32 on inlet stem 3 l Bag 30 has walls oi varying thickness in order that it may expand into substantially the shape of the article, expanding least for the sides of the article and most for the curved corners, and more for the ends which are further apart than for the sides which are closer together. Thus the bag is quite thick at 33 for the closely adjacent sides, is of less thickness at 34 for the less adjacent ends and is of still less thickness at 35 for the curved corners. In this way, pressure is exerted evenly over the entire inner surface of the article. The same effect may be obtained by varying the stretchability of the rubber in the bag walls. Less desirably, the bag may have uniform walls of uniform consistency. The bag may be preformed to approximate when collapsed the ultimate shape of the article, being slightly smaller than said ultimate shape.

Bag 30 may be inflated with any suitable fluid such as air under pressure, preferably to a pressure of 100 to 200 pounds per square inch. If it is desired to heat the article during molding, a hot fluid under pressure such as steam, or a hot liquid such as oil, diphenyl, diphenyl oxide, etc., is employed as the inflating fluid, either as the sole heating means or in addition to the employment of a heating medium in the outer mold members.

The veneer sheets indicated as 40 are precoated with a film 4! of adhesive which will act as a lubricant allowing the individual sheets to slide relative to one another during the molding. Instead of using veneer sheets, sheets 42 of flexible plywood having an adhesive coating 41 and sufliciently pliable to take the initial form may be employed (Figure 2), although the resulting article will not be quite as free of stress. Instead of precoating one side of each lamination as shown, every other lamination may desirably be coated on both faces, thereby simplifying the precoating operation. While the following description refers to using a plurality of veneer sheets 40, it will be understood that flexible plywood sheets 42 may be substituted for part or all thereof, if desired. The baseboard I is likewise initially provided with an adhesive coating Me. As will be seen by comparing Figures 3 and 4, baseboard i5 is adapted to be adhesively joined during the molding to the bottom of the completed article and to connect the ends of the plywood to form a closed article.

In carrying out a molding operation according to Figures 3 to 5, a pre-coated baseboard I5 is placed in the recess 43 of front wall 6 and a plurality of individual pre-coated veneer sheets 4|) of the same width and of gradually decreasing length are placed in the mold with their middle portions against rear mold wall 2 and their progressively inwardly shorter ends 44 projecting out at the sides of the mold. Ends 44 are then tucked into the mold into the position of Figure 3. End walls 4 are then moved inwardly and clamped at their innermost position by handles 25. Front wall 6 is then moved inwardly and clamped by means of handle 2 i. Lid I2 is then moved downwardly and locked with locking members l1. Steam is then admitted to cored passageways ii through inlet N to heat the mold, which is of metal, to the desired temperature, of say 250 to 300 F., but varying with the type of adhesive employed. Meanwhile bag 30 is inflated through inlet 8| to the desired pressure of to 200 pounds per square inch. The assembly is then allowed to stand until the adhesive has set, which will requirei'rom 2 to 20 minutes, but here again the time required will depend on the adhesive used and the temperature employed. The bag is then deflated, the mold cover opened, and the molded cabinet removed. If desired, a cabinet front 45 (Figure 5) of sheets of veneer or plywood out to correct shape and adhesively coated at its edges may be inserted on the formed article, the cover then closed, the bag re-ini'lated, and the mold allowed to stand until the front 45 is adhered. The attachment of the front oi the cabinet forms no part of the present invention and may be carried out in any manner.

In Figure 6 a modification is shown wherein the mold from; well 8 is not recessed, wherein the mold is not cored for heating and wherein the four sheets of veneer 40 are each cut to the exact ultimate length forming butt Joints which are staggered one on each side of the ultimate article.

In Figure 8, a modification is illustrated wherein the veneer sheets 40 are formed into a curved article with ends at right angles and with a curved stepped portion 46. A two-part uncored mold is shown, made up of movable hinged part 48 against which molding takes place and stationary part 41 being adapted to be clamped against mold part 48 by handle 2i and cam clamp i9. Bag 30 is formed with a very thick mold portion 49 adjacent step 48 where expansion is least and with thinner portions at other portions of the article graduated in accordance with the expansion effect. As before, bag 30 exerts forming pressure outwardly on the article. Preferably. as shown, bag 30 is inflated previously to some extent before insertion and before clamping of the mold parts in order to hold the sheets 40 in place.

In Figure 9, a still further modification is shown wherein sheets of veneer cut to proper length are used and a baseboard 5|! is employed which projects inwardly so as to expose sharp edges 5| which would injure the rubber bag 30 and prevent the bag from filling the portion 52 thereadjacent. To prevent this, a metal (heat-conducting) auxiliary mold member 53 is employed which is shaped outwardly to ilt insert ill and the portions of veneer sheets 40 thereadjacent to thereby transfer pressure evenly to the article and which is smooth on its inward face to fit bag 30. In this way, the production of a perfectly formed article is insured.

In Figures 10 to 12. a still further modification is shown wherein the laminations 40a and 40b are pre-cut to form a bottom or front portion 40c and side portions 40d and end portions Me. The intermediate lamination 40b is coated on both sides with adhesive 4! and the outer laminations 40a are uncoated. A cutout lllg is provided at each corner intersection of the sides and ends with the front to prevent the formation of an excessively compound curve at this point. The laminations are shaped into the five sided article in the manner illustrated in Figure 12, a curved member 9a being provided along each line of bend 4B), in order to give the desired curved configuration to the comers and to prevent unduly sharp bending. As before, the outward pressure of an expansible has 30 shapes the laminations into the final desired shape. Subsequently, the openings left between the edges of the sides 40d and the ends We may be filled in any desired manner as, for example, with a suitably shaped piece of wood.

It will be understood that I intend to include as within my invention such modifications as may be necessary to adapt it to varying conditions and uses and as fall within the spirit of the appended claims. For example, I may employ a thin flexible electrical heating element around the expansible bag to transmit the pressure of the bag to the article being formed while heating the same or may employ a metal internal mold member in a portion 01' the mold to transi'er the pressure from the bag to the article or I may use a layer of cloth, asbestos, metal foil or the like in place of a layer oi wood or in addition to the layers of wood. Similarly, while the above disclosure refers to liquid adhesive, I may use any adhesive in sheet form, such as "Tego glue film which is a dry film on a very thin tissue base and which is placed between layers of veneer rather than coated thereupon. This illm comprises a phenol-formaldehyde resin which polymerizes under heat, and moisture obtained from the veneers setting permanently after being subjected to heat for several minutes. Although such a dry film may not act as a lubricant for the veneer sheets, it does not in the least retard the sliding oi the individual sheets. I may also use other resins on the market which are allowed to dry after being spread on the veneer in liquid form and must be thoroughly dry before pressing, these resins usually requiring solvents other than water, such as alcohol or the like. In this way, I may avoid the use 01 aqueous liquid adhesives. the water of which may tend to swell or distort the sheets oi veneer. Whereas I have illustrated the use or three and four laminations, I am not limited to three or four ply articles, but may employ any number of plies, depending upon the thickness, strength or shape required.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Apparatus for shaping a plurality of forming individual flexible sheets of wood into an article of predetermined configuration comprising an outer mold adapted to have the sheets disposed therewithin in a form approximating the desired outer form of the completed product, and hold it against expanding outwardly and an inflatable member within the sheets positioned in said outer mold and adapted to exert forming pressure outwardly agaimt said sheets, said inflatable member having walls of varying thickness and disposed with the thickness of the walls inversely proportional to the extent of expansion required in order to exert evenlv distributed forming pressure. on the portions 01' the sheets located at diflerent distances from the center of the article to be formed, and means to expand said inflatable member.

2. An apparatus for shaping from a plurality of individual flexible sheets 0! wood an article 01' predetermined configuration, comprising an outer mold having a plurality of movable walls which when in closed position form an enclosed space. the opposed movable walls providing an access Opening in open position through which a sheets may be introduced into said mold space. and an inflatable member disposed with n and adapted to exert forming pressure outwardly against said sheets and having walls of varying thickness in accordance with the degree oi expansion required for exerting evenly distributed forming pressure on the portions of the sheet located at different distances from the center 01' the article to be iormed, and means to expand said inflatable member.

3. A method for forming a plurality of individual flexible sheets or wood into an article whose outer surface is of the same configuration as the shape or the form comprising the steps of arranging a plurality oi individual sheets of wood having adhesive therebetween within and along the walls of a hollow form in a tree and unattached adjacent relationship, oi simultaneously expanding the plurality of sheets outwardly against the inner surface of the form to shape the same into a laminated article having the configuration of the inside surface of the form, and 01' retaining the forming pressure upon the sheets until the adhesive therebetween has set, whereupon the article can be removed from the mold in a completely assembled condition.

4. The method of forming an article to a tinished shape directly from a plurality oi individual flexible sheets of wood which comprises; precutting a plurality of individual flexible sheets of wood adapted to cooperate with one another to be shaped into the contour of a finished laminated article; arranging the plurality o! individual pre-cut sheets of wood with adhesive therebetween within a hollow form in a tree and unattached adjacent relationship in a manner that v the pre-cut sheets are disposed with respect to each other in a selected layer arrangement determined by the relative sizes of the pre-cut sheets, the size of the sheets gradually diminishing as they approach the interior oi the form, to position them in their proper layer relationship; simultaneously pressing the plurality of sheets outwardly against the inner surface of the form to cause them to assume their proper final relationship with respect to one another to shape the same into a laminated article having the configuration oi the inside surface of the form; and retaining the forming pressure upon the sheets until the adhesive therebetween has set. whereupon the article can be removed from the mold in a completely assembled condition and in its finished shape.

CLARENCE U. GRAMELBPACHER. 

